The invention relates to a process for producing a clothing wire for open-end spinning.
Open-end spinning (OE spinning) is currently the most economic process for producing yarns from short fibers. Approximately one third of global production of yarns of this type uses the OE spinning process. There are approximately 6 millions OE spinning units in operation.
The most essential components of the open-end spinning unit are the opening cylinder and the spinning rotor. The opening cylinder separates the feed sliver into its individual fibers, just a few micrometers thick, removes impurities and feeds the fibers through a feed tube into the spinning rotor, where they are reassembled to form a yarn. The working of the opening cylinder has a crucial bearing on the stability of the spinning process and on the quality of the yarn product.
A common form of opening cylinder is a cylindrically shaped base body made from aluminum or steel, whose circumferential surface is equipped with a helical slot fitted with a finely toothed steel tapexe2x80x94the wire clothingxe2x80x94fixed in place by calking. FIG. 1 shows a partly cut-away opening cylinder comprising an aluminum base body 1 and the clothing wire spiral 2.
Examples of opening cylinders and toothed tapes or wires may be found inter alia in U.S. Pat. Nos. 2,937,413, 4,233,711, 2,731,676, 4,435,953 and 3,833,968. The toothed tapes (xe2x80x9cclothingsxe2x80x9d) are usually produced by rolling an initially round wire into a profile tape with the characteristic cross-sectional shape (see FIG. 2a) and then stamping out the teeth from the flat part of this profile tape. Such a clothing wire is shown in cross section in FIG. 2a and in a partial side view in FIG. 2b. Sometimes the tooth flanks are subjected to a mechanical after-treatment by grinding. This is described for example in U.S. Pat. No. 4,233,711.
A clothing wire obtained after these production steps is referred to as a raw wire. A wire of this type is commercially available, for example under the name OE-M-3325 CSH from Graf/CH-Rapperswil. The edges of the teeth of the raw wire are sharp and in part very rough. Opening cylinders equipped with a clothing wire in this state have completely unacceptable spinning characteristics, since the fine fibers are destroyed by the raw wire or become lodged in the rough areas of the teeth, only to become detached from time to time and create thick places in the yarn product.
It is therefore common practice to subject the raw wires, prior to mounting as clothing wire on the base body, to a material-removing process comprising an electrolytic or chemical treatment. To this end, the raw wire is successively degreased, descaled, pickled and deburred in various electrolytic and/or chemical baths. Thorough rinsing is necessary between the actual operations. These treatment steps serve to round the sharp edges of the raw wire and to generally improve the surface quality. However, the entire process is laborious and costly.
Since particularly high demands are imposed on the dimensional accuracy of the clothing wire for OE opening cylinders, this wire is generally not treated electrolytically, but rather by the more complex chemical deburring process.
The surface state of the teeth resulting from this treatment is known as needle finish. It is considered absolutely mandatory for satisfactory working of an opening cylinder equipped with wire clothing. A reference to this needle finish may be found for example in U.S. Pat. No. 5,006,367, column 2, lines 9-10.
It is also common practice to protect the teeth of the clothing wire of opening cylinders from wear, and hence to prolong the useful life of opening cylinders by specific surface-technological measures. A particularly effective measure is the application to the needle-finished, wire-clothed opening cylinder of a dispersion layer consisting of autocatalytically deposited nickel with embedded diamond particles. This is described inter alia in Metalloberflxc3xa4che 1984, No. 4, page 139 or Textile Month, May 1981. Opening cylinders equipped with such a nickel-diamond coating have service lives which exceed those of uncoated opening cylinders by a factor of from five to ten.
Like the above-described deburring and rounding treatment of raw wire, a nickel-diamond coating requires a multistage treatment in dip baths, so that it is desirable to combine the two time-consuming, expensive processes in an economical manner.
A corresponding process for providing opening cylinders which have a raw wire clothing with a needle finish and a diamond coating in a single pass is described, for example, in DE 4314161 A1 (corresponding to U.S. Pat. No. 5,547,709).
When the clothing wire is rolled into the helical slot of the cylinder base body (xe2x80x9cclothingxe2x80x9d), uncoated, straight wire is introduced from relatively large reels, under considerable tension, into the slot of the slowly rotating cylinder body and is clamped at the sides by mechanical deformation of the web between the turns of the slot by means of narrow rollers. During this operation, the clothing wire undergoes considerable plastic deformation in the region of the tooth base, since it is considerably stretched in this area. In the case of uncoated wire, this does not cause any problems, but a coating which is already on the wire before it is rolled into place, in particular the diamond coating which is typical of opening cylinders, would inevitably crack and even flake off in the event of plastic deformation of the base material of this nature. This would be altogether unacceptable for working of the cylinder. To avoid this problem, therefore, cylinders which have been provided with the clothing wire (xe2x80x9cclothed cylindersxe2x80x9d) are provided with a nickel-diamond coating.
In DE-A 2433769, it has been proposed for clothing wire to be helically preshaped, with a diameter similar to the diameter of the cylinder body, and for this wire then to be fixed to the cylinder body.
A preshaped wire of this type may also already have been coated before being fitted to the cylinder body, as described, for example, in EP 0861930. According-to the prior art, however, the wire must have the needle finish required for the spinning process even before it is rolled into place, since the process which results in this surface state cannot be controlled on tightly coiled wires.
Since diamond coating of the required quality has only been mastered by a few commission processors throughout the world, it is necessary for the cylinders which have already been fitted with the clothing wire or the precoiled, needle-finished wire to be transported to the commission processor and then transported back to the OE machine manufacturer following the treatment.
Because of this very laborious production sequence, providing opening cylinders for the end user is very expensive and involves inordinately long delivery times.
The entire sequence is not only time-consuming and expensive, but also involves a considerable risk of rejects, since even slight impacts on the clothing wire tips, which are often inevitable in the numerous handling operations which are still to take place after the clothing has been fitted, to the cylinder may lead to deformation and make the cylinder unusable.
Preferred materials used for the cylinder base body are aluminum alloys, for weight reasons. Nickel-diamond coating of the cylinder body is not necessary, since it is not exposed to any significant wear and aluminum materials are usually also sufficiently corrosion-resistant.
The present invention is based on the object of providing a process which allows rapid and inexpensive production of opening cylinders for OE spinning.
The object is achieved by a process for producing a clothing wire which is suitable for fitting to an opening-cylinder base body, wherein a raw wire which is customarily used to produce clothing wire is processed on end to form a wire coil, in which the teeth of the wire are perpendicular to the coil axis and which has a diameter which corresponds to the diameter of the opening-cylinder base body or differs by at most xc2x15% from the diameter of the opening-cylinder base body, and the wire coil is pushed loosely onto a support device and, together with this device, is introduced into plating unit, the process steps which are customarily used for the deburring of the raw wire and the nickel-diamond coating of a clothed opening cylinder taking place in the plating unit, and the clothing wire being removed from the plating unit.
The process according to the invention allows the manufacturer of opening cylinders to reduce the delivery time for cylinders based on the customer""s specification from approximately 8 weeks to approximately 4 weeks without it being necessary to hold a considerable stock of expensive needle-finished clothing wire. In addition, direct cost savings are achieved by a reduction in the reject rate caused by damage and by eliminating the need for complete cylinders to be transported from manufacturer to nickel-diamond coating plant.
Starting from inexpensive raw wire, the process according to the invention provides a clothing wire which has been optimized in accordance with the customer""s specification, has the active geometry of the clothing wire tips which is required for the cylinder to function optimally, at lower costs than those involved in the prior art, and bears the nickel-diamond coating which is required for the required long-term spinning performance to be achieved.